An actuator device including a piezoelectric element configured to be displaced by application of a voltage is used as liquid ejecting means of a liquid-jet head mounted on a liquid-jet apparatus for injecting droplets, for example. As for the liquid-jet apparatus described above, there is known an inkjet recording device including an inkjet recording head, which is configured to construct part of a pressure generating chamber communicating with a nozzle orifice by use of a vibration plate, to pressurize ink in the pressure generating chamber by deforming this vibration plate with a piezoelectric element, and thereby to eject ink droplets out of a nozzle orifice.
Two types of inkjet recording heads are put into practical use, namely, one mounting an actuator device of a longitudinal vibration mode configured to expand and contract in an axial direction of a piezoelectric element, and one mounting an actuator device of a flexural vibration mode. Moreover, as the one applying the actuator device of the flexural vibration mode, there is one configured to form a uniform piezoelectric film across the entire surface of the vibration plate in accordance with a film forming technique, and to form piezoelectric elements independently of respective pressure generating chambers by cutting this piezoelectric layer into shapes corresponding to the pressure generating chambers in accordance with a lithography method, for example.
As a material of a piezoelectric material layer constituting such piezoelectric elements, lead zirconate titanate (PZT) is used, for example. In this case, when sintering the piezoelectric material layer, a lead component of the piezoelectric material layer is diffused into a silicon oxide (SiO2) film, which is provided on a surface of a passage-forming substrate made of silicon (Si) for constituting the vibration plate. Accordingly, there is a problem that the melting point of silicon oxide drops by diffusion of this lead component and silicon oxide melts away owing to the heat at the time of backing the piezoelectric material layer. To solve this problem, for example, there is a technique configured to construct a vibration plate on a silicon oxide film, to provide a zirconium oxide film having a predetermined thickness, to provide a piezoelectric material layer on this zirconium oxide layer, and thereby to prevent diffusion of a lead component from the piezoelectric material layer into the silicon oxide film (see Patent Document 1, for example).
This zirconium oxide film is formed for instance by forming a zirconium film in accordance with a sputtering method and then subjecting this zirconium layer to thermal oxidation. For this reason, there is a problem of occurrence of defects, such as occurrence of cracks on the zirconium oxide film due to stress generated at the time of subjecting the zirconium film to thermal oxidation. Meanwhile, if a large difference in stress exists between the passage-forming substrate and the zirconium oxide film, there also occurs a problem that the zirconium film comes off after forming the pressure generating chambers on the passage-forming substrate, for example, due to deformation of the passage-forming substrate and the like. Patent Document 1: Japanese Unexamined Patent Publication No. 11(1999) - 204849 (FIG. 1, FIG. 2, p. 5)